MAT253气体同位素质谱仪测定微量氢同位素组成进样方法初探  

An Improved Sampling Method for Measurement of Trace Hydrogen Isotopic Composition by MAT 253 Gas Isotope Mass Spectrometer

作　　者：孟庆强[1,2] 金之钧[1] 刘文汇[1,3] 陶成[3] 把立强[3] 杨华敏[3] 

机构地区：[1]中国石油化工股份有限公司石油勘探开发研究院油气勘探研究所,北京100083 [2]中国地质大学能源学院,北京100083 [3]中国石油化工股份有限公司石油勘探开发研究院无锡石油地质研究所,江苏无锡214151

出　　处：《岩矿测试》2010年第6期639-642,共4页Rock and Mineral Analysis

基　　金：中国博士后科学基金项目资助(20100470500);国家重点基础研究发展计划("973"计划)项目资助(2005CB422102);中国石油化工股份有限公司科技部项目资助(G8804-07-ZS-0018)

摘　　要：幔源流体活动区天然气中微量H2是研究幔源H2同位素组成的最佳样品,但受目前测试技术的限制,能准确测试同位素组成的H2浓度下限仍然有待继续降低。前人研究表明,当H2浓度低于1.5%时,测试结果的误差较大,可信度较低,这可能与载气进样时在进样针孔附近发生了随机分馏有关。为了避免这种随机分馏,文章提出了一种利用压差进样的方法,即利用饱和NaC l溶液增加样品瓶内的压力实现进样。实验结果表明,利用这种进样方法,不同浓度条件下,H2同位素组成测试值的极差与标准偏差都随H2浓度的增加而减小,统计得到的绝对误差与仪器的误差范围相当。因此,该进样方法可以有效避免微量H2在进样过程中发生的随机分馏,提高测试结果的精度和可信度。同时表明可以对现有设备进行合理改造,挖掘仪器的测试潜能。The trace hydrogen in the natural gas from the mantle-derived fluid areas is the best specimen to reveal the isotopic composition characters of mantle-derived fluids.Restricted by the present measurement methods,the detection limit of hydrogen for accurate measurement of hydrogen isotopic composition should be further improved.It was proved that the measurement error of hydrogen isotopes was relatively larger and the reliability of the measurement results deteriorated when the hydrogen content was lower than 1.5%,which may relate to the random fractionation of hydrogen isotopes around the inlet needle when it was sampled by the carrier gas.In order to avoid this random fractionation,an improved pressure sampling method was brought out,that is,increasing the pressure inside the sample container by pumping in salt-saturated water.The experiment results showed that by this sampling method the range and the standard deviation of the measured hydrogen isotope values declined with the increasing of the hydrogen content within 1% range and the absolute error was equivalent to that of the system error of MAT 253 instrument.Thus,this sampling method could effectively avoid the random fractionation of hydrogen isotopes during the sampling and improve the accuracy and reliability of the measurement results.It was also proved that the presently employed machine could be reasonably improved in order to enhance its function.

关 键 词：微量氢 进样方法 同位素测试 

分 类 号：O613.2[理学—无机化学] TE135.4[理学—化学]